(a) Field of the Invention
The present invention relates to a frequency reconfiguring antenna design technique. More particularly, the present invention relates to a technique for changing an antenna element configuring an array in order to improve array performance of a frequency reconfiguration array antenna.
This work was supported by the IT R&D program of MIC/IITA [2007-F-041-01, Intelligent Antenna Technology Development].
(b) Description of the Related Art
A reconfiguration antenna can vary antenna parameters such as frequency, polarization, and pattern by electrical or mechanical control, and a frequency reconfiguration antenna is reconfigured to be operable in at least two different frequency bandwidths. In this instance, when configuring the frequency reconfiguration antenna element (hereinafter, antenna element) as an array antenna, the array interval is fixed with reference to a single frequency, in general, the center frequency of the intermediate bandwidth in the entire reconfiguration bandwidth.
In this instance, array performance of the frequency reconfiguration array antenna is determined by a radiation pattern that is expressed in Equation 1.Ptotal(ω)=Pelement(ω)×AF(ω)  (Equation 1)
Here, Ptotal(w) is a radiation pattern of the entire array antenna, Pelement(w) is a radiation pattern of the antenna element which is a single element, and AF(w) is an array factor. The array factor is determined by a physical gap between antenna elements, intensity ratio of signals supplied to the respective antenna elements, and phase difference. The radiation pattern and the array factor of the antenna element are variable by the frequency, and hence the radiation pattern of the entire frequency reconfiguration array antenna is also variable by the frequency.
The array performance of the frequency reconfiguration array antenna is determined by an array gain determined by the radiation pattern, a beam width, a size of a side lobe, and beam efficiency of the radiation pattern.
In this instance, since the frequency reconfiguration antenna element has a different area of a radiator according to the frequency bandwidth, it has a relatively uniform gain in the reconfigured frequency bandwidth, differing from the wideband or multiband antenna. When the antenna element having a constant gain reconfigures the frequency bandwidth by using a high frequency bandwidth, the beam efficiency is reduced because of the increase of the side lobe, and hence the array performance in the high frequency bandwidth can be reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.